<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width:200px;
      height: 100px;
      background-color: red;
      position: absolute;
      z-index: 1;
    }
    #d2{
      width: 100px;
      height: 200px;
      background-color: blue;
      position: absolute;

      z-index: 2;/*后执行的会覆盖在上方,值越大显示越靠前*/
    }
  </style>
</head>
<body>
<div id="d1"></div>
<div id="d2"></div>
</body>
</html>